Low temperature lubricants



Patented Aug. 15,

UNITED "STATES PATENT ori-lei:

2 Low ramna imwaarcmrs 2 Cities ServlceOil Company, New York, N. Y., acorporation of Pennsylvania No Drawing.

method of lubricating metallic bearing surfaces of various types ofmechanisms at excessively low temperatures, and to an improved lubricanttherefor.

More particularly, the improved lubricant preferably consists of a,single compound adapted to be an eifective lubricant at extremely lowtemperatures of for example about 100F. below freezing temperature, andalso to be eflective at high temperatures of the order of 100 or 200'13. Ordinary lubricating oils do not provide effective lubricants atsuch low temperatures or over such wide temperature ranges.

The need for lubricants of the type of the present invention is apparentfrom the tact that aircraft and other mechanisms are operated at widelydifferent temperature within very short periods of time. For example, anaeroplane may take oil at a ground temperature of 100 F. or 140 F. andwithin a matter of minutes be operating at temperatures of the order ofminus 40 F. (72 F. below freezing) or lower. Other mechanisms must beused almost continuously at low temperatures, as for example motorvehicles used in the Arctics. Sometimes it is impossible to operate amechanism in a frigid climate or under conditions of extreme cold untilthe bearings have been warmed artificially.

The primary object of the present invention is to provide a method forlubricating metal bearing surfaces and to provide a lubricant which willavoid the above difliculties encountered in the use of ordinarylubricating oils.

The present invention includes the discovery that the monopropylbenzenes have the unique properties required for the lubrication ofhearing surfaces over wide temperature ranges of the type referred toabove and at extremely low temperatures, although it is ordinarily notexpected that a material which would be a satisfactory lubricant at atemperature of minus 70 F. would.

also be satisfactory, and have a satisfactory viscosity when used attemperatures of 100 F. or 200 F.

The monopropyl benzenes, cumene' (isopropyl benzene), and isocumenein-propyl benzene) have a load-carrying capacity about equal to that ofa Pennsylvania motor oil (30 SAE). Cumene, the preferred lubricant, hasthe followingproperties:

Viscosity at minus 40 F centistokes 4.20

Viscosity at F do 2.48 Viscosity at 100 F ..do 0.90

Viscosity at 200 F do 0.58 Boiling point ..F 308 Melting point F Minus142 Specific gravity 0.864 Refractive index 1.4930

Chemical stability "i Excellent Application September 16, 1942,Serial-No. 458,564

16 Claims-j (c1; 252-59) I Isocumene has properties comparable to thatof cumene, the boiling point being slightly higher and the melting pointslightly lower. Both compounds are colorless liquids insoluble in water.

The improved lubricant according to the present invention may be applieddirectly to the bearings to be lubricated in any suitable mannercommonly used for the application of liquid mineral lubricating oils.Theimproved lubricant is pref-- erably used undiluted with othermaterials. but

may be applied for certain types of bearings as a grease. Suitablegreases may be made from calcium, aluminum or sodium soaps as thickeningagents. The soaps may be the stearate, oleate or derivatives of othersuitable fatty acids. A suitable grease may be made by the use of from4% p to 20% of soap or other thickening agent, the reapproximately 1%mainder being cumene, isocumene or a mixture of the cumenes.. Up to thepresent time, it has been found impossible to make a grease with lithiumsoap. Greases which are to be used under extreme pressure conditionsshould include of an extreme pressure agent such as Polane," tricresylphosphate, sulfurized tricresyl phosphite, a sulfurized animal oil, orother suitable E. P." agent. The lubricant either when used aloneor'in'a grease composition may include tricresyl phosphite,triethanoiamine, or

,other known anti-corrosion agent, especially where the bearings areconsiderably exposed to the action'of the air or other oxidizing orcorrosive atmosphere.

While the improved lubricant of thepresent invention provides effectivelubrication over a wide temperature rangeincluding extremely lowtemperatures, it may be found desirable to provide a definite viscositycurve over a specific, relatively narrow temperature range, in whichcase the cumene of the present invention may be blended with decalin ortetralin in proportions adapted to give the desired viscosity curve. Inmaking these compositions, the major part of the mixture is preferablycomprised of cumene with the balance made up of decalin oi tetralin.

While the features of the present invention have been described andillustrated in connection with certain examples, it is to be understoodthat the invention is not to be restricted except in acing viscositycharacteristics adapted to provide eifective lubrication at extremelylow temperatures as well as at temperatures above normal atmospherictemperature, consisting essentially of a monopropyl benzene and asmallproportion of an extreme pressure agent adapted to impart extremepressure properties to the lubricant.

A lubricant as defined by claim: 1, consisting cumene comprises a inadorproportion of the essentially of isopropyl benzene. 1 lubricant.

' 3. A lubricant as defined by claim 1 essentially of n-propyl benzene.4. The method of lubricating bearings oi mechanisms operated at sub-zerotemperatures comprising applying to the bearings a fluid lubricantconsisting essentially of a monopropyl benzene.

, 5. The method 01 lubricating bearings as defined by'claim 5 in whichsaid monopropyl benacne is cumene.

,6. The method 01 lubricating bearings as defined by claim 5 in whichsaid monopropyl ben zene is isocumene.

"I. The method of lubricating relatively moving 'coi sisting ii'rnemethod as defined by claim 9 m which said lubricant is comprisedessentially of cumene .j lcontaining a relatively small proportion of anextreme pressure agent sufilcient to greatly increaso'the load-carryingcapacity of the cumene.

12. A grease for lubricating metallic bearing surfaces comprising fromabout 4% to about 20% bearing surfaces over temperature ranges such thatan ordinary lubricating oil will be unable to provide effectivelubrication, which comprises maintaining on such bearing surfaces alubricant preeminently consisting of cumene.

8. In the lubrication or mechanisms operated over wide temperatureranges of from approximately minus F. to upwards of 100 1"., a inbricantconsisting essentially of a monopropyl benzene applied to the bearings01' such mechanism.

9. The method of lubricating relatively moving bearing surfaces overtemperature ranges of ap-' proximately 270 F. extending to temperaturesas low as approximately minus 70 F., these ranges being such thatanordinary lubricating oil will,

be unable to provide eii'ective lubrication, which comprises maintainingon such bearing surfaces a lubricant, the major proportion of which is amonopropyl benzene.

10. The method as defined by claim 0 in which of a thickening agent, andfrom about 96% to about 80% of a monopropyl benzene.

- 13. A grease for metallic bearing surfaces comprised mainly ofamonopropyl benzene and a thickening agent in suilicient proportion toform a grease. v

14; A grease for lubricating metallic bearing surfaces comprised mainlyoi a monopropyl benzene, a thickening agent and an extreme pressureagent.

15. A lubricant for metallic bearing surfaces having viscositycharacteristics adaptedto provide efiective lubrication at extremely'iowtemperatures as well as at temperatures above normal atmospherictemperature, consisting essentially of z a monopropyl benzene containinga small propontion of an anti-corrosion agent for protecting metalsurfaces.

16. The method oi lubricating relatively moving bearing surfaces, whichcomprises maintaining on such bearing surfaces a lubricant preeminent'lyconsisting of a monopropyl benzene containing-asmall proportion oi ananticorrosion agent for protecting the bearing surfaces.

JOHN D. MORGAN.

